Samsung Power Supply Board BN44-00874F

[nomoresonys]

Is it fair to say ICM801CS (FA6B22N, cannot find a datasheet) should be driving QM801CS and QM802CS when the board is in standby? It's switching the 170vdc of the filter caps, to ultimately provide an unboosted VDC on the output connector (7ish volts)?

In the current state with the board on the bench and plugged in, on ICM801CS pins:

1 - 68-69VDC
2 - 0vdc
3 - 0vdc
4 - 7.2VDC
5 - 0vdc
6 - 0vdc
7 - 0vdc
8 - 0vdc
9 - 0vdc
10 - 10VDC
11 - 0vdc
12 - GND
13 - 0vdc
14 - 8VDC
15 - 8VDC
16 - 10VDC

https://products.fujielectric.com/en...etail/FA6B22N/

This link is the most info I could find for this IC.

Thoughts?

Something doesn't seem to be matching, you have pin 12 as GND but in the datasheet you posted, pin 12 is VCC.

[nomoresonys]

So you're saying the datasheet you posted is not the right one?

[lotas]

12 pin is GND, and VCC is 10 pin.

[nomoresonys]

Ok, not exactly sure but might be able to get a clue by testing resistance from neg. leg of filter cap to pin 10 VCC, see what you get, done with tv unplugged from power.

[nomoresonys]

It was Nicks datasheet that said 12 pin is VCC.

[Nicktronic]

It was Nicks datasheet that said 12 pin is VCC.

I just checked again, what lotas posted in #23 is from the document I attached. 10 is VCC. Regardless, I will check what you suggested in post #24, thank you.

Does the 7VDC on FB indicate a problem?

[Nicktronic]

Ok, not exactly sure but might be able to get a clue by testing resistance from neg. leg of filter cap to pin 10 VCC, see what you get, done with tv unplugged from power.

400-500 Kohms

[nomoresonys]

I am not mistaken in this case, in post #10, the datasheet clearly labels pin 12 as VCC, so it must not have been a match to your IC.

[nomoresonys]

400-500 Kohms

Ok, this is good, that IC may be alright.

[nomoresonys]

What do y'all think? seeming like a capacitor issue maybe?

[lotas]

UCC28064A and FA6B22N are completely different microcircuits and we were talking specifically about FA6B22N.

[Nicktronic]

I am not mistaken in this case, in post #10, the datasheet clearly labels pin 12 as VCC, so it must not have been a match to your IC.

Oh, lol, we are talking about two different ICs....I'm talking about the FA6B22N and you are talking about UCC28064A

[nomoresonys]

That explains it, picture was not very clear.

[nomoresonys]

Maybe reflow the solder joints on the transformers and anything on a heatsink or any others that may need it, just in case it's a simple thing like that.

[nomoresonys]

Maybe check DM807 and that little transistor next to it.

[nomoresonys]

Can you post a good clear picture of that IC and the mosfet area you replaced? can be two pictures just need a little more detail.

[nomoresonys]

Make sure none of the resistors are bad or have risen in value, it doesn't take much to mess up the balance.

[Nicktronic]

Let me know if these are sufficient

[Nicktronic]

Maybe check DM807 and that little transistor next to it.

Did already, they are good.

[nomoresonys]

Guess this ones too tough for me, maybe test all your blue ceramic caps on top of board, test them in ohm mode in circuit, they should probably read in the m or k ohms. They can be bad and not show externally, I assume you did check all the solder joints paying extra attention to transformers and things on heatsinks, the joints can get micro-cracks that are not easily detected. Just tried this test but didn't work on my meter tho.